Light emitting diode package with metal reflective layer and method of manufacturing the same

ABSTRACT

The invention relates to an LED package having a metal reflective layer for focusing and emitting light through a side of the package, and a manufacturing method of the same. The LED package includes a substrate with an electrode formed thereon, a light emitting diode chip disposed on the substrate, and an encapsulant covering the LED chip and the substrate to protect the LED chip. The LED package also includes a metal reflective layer surrounding side surfaces of the encapsulant to form a light transmitting surface on a top surface of the encapsulant. The invention minimizes light loss, improves luminance, can be mass-produced as a PCB type, and adopts EMC transfer molding to minimize irregular color distribution, thereby improving optical quality.

CLAIM OF PRIORITY

This application claims the benefit of Korean Patent Application No.2005-53163 filed on Jun. 20, 2005, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a Light Emitting Diode (LED) packagehaving a metal reflective layer for focusing and emitting light throughone side of the package, and a method of manufacturing the same. Moreparticularly, the invention relates to an LED package with a metalreflective layer minimized in light loss and improved in luminance,which can be mass-manufactured as a PCB type in a small size unaffectedby the size of an LED chip, and is improved in productivity.

2. Description of the Related Art

In general, a mobile phone or PDA adopts a light emitting diode (LED)package in various sizes for a backlight.

As the backlights are becoming slimmer, the LED packages adopted thereinare also becoming slimmer these days.

The LED package 300 shown in FIG. 1 is described in U.S. Patent No.2003-0094622, in which a reflective layer 312 is formed of a lead framefor an LED chip 310 mounted in the package 300, and the package issealed with a sealing plate 314 that covers the LED chip 310 and thereflective layer 312.

In this conventional LED package 300, the reflective layer 312 is madeof an Ag-plated layer to focus and emit light from the LED chip 310through one side of the package.

However, in such a conventional structure, the LED chip 310 is formed ina recess 322 of the substrate, and a separate sealing plate 314 coversthe recess 322, and thus limiting automated manufacturing andmass-production.

FIGS. 2(a) and 2(b) illustrate a different structure of LED package 400of the prior art. An LED chip 412 is mounted on a substrate 410, and amolded part 414 with a cavity therein is adhered on the substrate 410.Then, a resin solution with phosphor and epoxy mixed therein is injectedinto the space 414 a to be cured, and the complete structure is diced.However, as an additional process is required to adhere the molded part414 on the substrate 410, the manufacturing process is not efficient interms of productivity.

In addition, as shown in FIG. 3, in the conventional LED package 400,the resin solution with the phosphor and epoxy mixed therein is injectedinto the space 414 a in the molded part 414 and cured for about 1 hourto form an encapsulant 416. In such a curing process, the phosphor inthe epoxy 418 a of the encapsulant 416 tends to precipitate, causingirregular color distribution. Therefore, such a conventional LED package400 yields low-uniformity and rather mediocre color development.

SUMMARY OF THE INVENTION

The present invention has been made to solve the foregoing problems ofthe prior art and therefore an object of certain embodiments of thepresent invention is to provide an LED package having a metal reflectivelayer, which does not require a molded part, and thus can have a minimalthickness, and a method of manufacturing the same.

Another object of certain embodiments of the invention is to provide anLED package having a metal reflective layer, which can be mass-producedwithout being affected by the LED chip size, and can be easilymanufactured in a small size, and a method of manufacturing the same.

Further another object of certain embodiments of the invention is toprovide an LED package having a metal reflective layer, which adoptsEpoxy Molding Compound (EMC) transfer molding to minimize irregularcolor distribution and enhance uniform color development, and a methodof manufacturing the same.

Yet another object of certain embodiments of the invention is to providean LED package minimized in light loss and improved in luminance, whichcan be mass-produced and is improved in productivity, and a method ofmanufacturing the same.

According to an aspect of the invention for realizing the object, thereis provided a light emitting diode package for emitting light from alight emitting diode chip in one direction, including: a substrate withan electrode formed thereon; a light emitting diode chip disposed on thesubstrate; an encapsulant covering the LED chip and the substrate toprotect the LED chip; and a metal reflective layer surrounding sidesurfaces of the encapsulant to form a light transmitting surface on atop surface of the encapsulant.

According to another aspect of the invention for realizing the object,there is provided a method of manufacturing a light emitting diodepackage for emitting light from a light emitting diode chip in onedirection, including steps of: providing a substrate with an electrodeformed thereon; disposing a light emitting diode chip on the substrate;forming an encapsulant on the light emitting diode chip and thesubstrate; cutting the encapsulant; and forming a reflective layer onthe encapsulant.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a sectional view illustrating an LED package according to theprior art;

FIG. 2 illustrates another LED package according to the prior art, inwhich (a) is an explanatory view illustrating cutting a molded part, and(b) is a longitudinal sectional view;

FIG. 3 illustrates a work process with epoxy resin constituting anencapsulant of the LED package according to the prior art;

FIG. 4 is a configuration view illustrating an LED package having ametal reflective layer according to the present invention, in which (a)is a perspective view of the exterior, and (b) is a sectional viewillustrating the LED package having a light transmitting surface on anupper part thereof;

FIG. 5 is a view illustrating the step-by-step process of manufacturingthe LED package having a metal reflective layer according to the presentinvention;

FIG. 6 is a view illustrating the step-by-step process of manufacturinga variation of the LED package having a metal reflective layer; and

FIG. 7 is a view illustrating EMC transfer molding to form anencapsulant in the manufacturing process of the LED package according tothe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferred embodiments of the present invention will now be described indetail with reference to the accompanying drawings.

As shown in FIG. 4, an LED package 1 having a metal reflective layeraccording to the present invention is for emitting light from an LEDchip 5 in one direction of an encapsulant 10.

Light is emitted through a light transmitting surface 17 which ispreferably in front and in parallel with a plane where the LED chip 5 isdisposed.

The LED package 1 having a metal reflective layer according to thepresent invention has a substrate with electrodes 15 a and 15 b formedthereon. The substrate 15 may preferably be a Printed Circuit Board(PCB) or a ceramic substrate having pattern electrodes 15 a and verticalelectrodes 15 b such as vias.

In addition, an LED chip 5 is electrically connected to the electrode 15a and mounted on the substrate 15. The LED chip 5 may be a horizontaltype with all of its electric terminals formed only on an upper surfacethereof, or a vertical type with the electric terminal formed on upperand lower surfaces thereof.

In addition, an encapsulant 10 is formed on the LED chip 5 and thesubstrate 15 to cover them. The encapsulant 10 is made by curing epoxyresin, and preferably is formed via Epoxy Molding Compound (EMC)transfer molding using epoxy molding compound with phosphor mixedtherein in order to minimize irregular color distribution.

According to the present invention, when the encapsulant 10 is disposedon the LED chip 5 and the substrate 15 in a desired form, a reflectivelayer 20 is formed on the encapsulant 10 with a light transmittingsurface 17 on one surface, i.e., an upper surface of the encapsulant 10as shown in FIG. 4 (b).

The reflective layer 20 is made of metal selected from a groupconsisting of Al, Au, Ag, Ni, W, Ti and Pt. The reflective layer 20 isformed on side surfaces of the encapsulant 10 via electroless plating orelectro-plating, or surrounding the entire surfaces of the encapsulant10 via vacuum deposition, with an upper surface of the encapsulantpolished to form the light transmitting surface 17.

Therefore, the reflective layer 20 surrounds the entire side surfaces,except the portion of the light transmitting surface 17, of theencapsulant 10 without any spots missed.

A manufacturing process 100 of an LED package having a metal reflectivelayer according to the present invention will now be explainedhereinafter.

As shown in FIG. 5, the manufacturing process 100 of the LED packagehaving a metal reflective layer according to the present inventionstarts with a step 102 of providing a substrate 15 with electrodes 15 aand 15 b formed thereon.

In addition, the substrate 10 is provided with pattern electrodes 15 aand vertical electrodes 15 b such as vias for supplying power to the LEDchips and electrodes 15 c for plating a reflective layer later.

The substrate 15 can be a PCB or a ceramic substrate with verticalelectrodes 15 b such as vias formed thereon, and each of the patternelectrodes 15 a connected to the LED chip 5 is electrically connected toeach of the vertical electrode 15 b such as a via.

In the next step 104, the LED chip 5 is mounted on the substrate 15.

In this step 104, a plurality of LED chips 5 are simultaneously mountedon predetermined locations on one substrate 15, and each of the LEDchips 5 is electrically connected to each of the pattern electrodes 15 aon the substrate 15 via wires.

In the next step 106, an encapsulant 10 is formed on the LED chip 5 andthe substrate 15.

In this step 106, the encapsulant 10 is formed via EMC transfer moldingusing an epoxy molding compound with phosphor mixed therein in order tominimize irregular color distribution after it is cured.

As shown in FIG. 7, in the process of EMC transfer molding 200 adoptedfor forming the encapsulant 10, the substrates 15 and the LED chips 5are inserted into a mold 210 maintained at about 150° C. to 190° C., anda solid mixture 220 of transparent EMC and phosphor maintained at about80° C. to 90° C. is injected into the mold 210. Then, the mixture 220 ofthe transparent EMC and the phosphor is compressed at 500 to 1000 psi sothat the mixture of the transparent EMC and the phosphor changes in itsphase from solid to liquid inside the mold 210. This liquid mixture 220of the transparent EMC and the phosphor flows over the substrate 15 andthe LED chip 5 to form the encapsulant 10. After 5 to 7 minutes withoutapplying heat and compression, it is cured in a short time from liquidphase to solid phase.

After the curing is completed, the substrate 15 and the LED chip 5 withthe encapsulant 10 formed thereon is separated from the mold 210 tocomplete the encapsulant 10.

In the encapsulant 10 formed via the above described EMC transfermolding, the phosphor 222 b does not precipitate in the transparent EMC222 a, which minimizes irregular color distribution and enhancesuniformity of color development.

After the encapsulant 10 is completed, the encapsulant 10 is cut in thenext step 108.

In this step 108, in order to form a desired shape of encapsulant 10 forthe LED chips 5, only the encapsulant 10 is diced or etched. In thisstep 108, the encapsulant 10 is formed such that the lower peripherythereof exposes the electrode 15 c for plating.

Then, a reflective layer 20 is formed on the encapsulant 10 in the nextstep 110. The reflective layer 20 is formed as a plated layer 22 on theencapsulant 10 by electroless plating or electro-plating highlyreflective metal selected from a group consisting of, for example, Al,Au, Ag, Ni, W, Ti and Pt. At this point, the plated layer 22 is formedintegrally with the encapsulant 10 to completely surround the sidesurfaces of the encapsulant 10, thereby preventing leakage of light.

With the reflective layer 20 formed as just described, the lighttransmitting surface 17 is formed on an upper surface of the encapsulant10.

In the next step 112, the plated layer 22 and the substrate 15 are cuthorizontally and vertically into individual LED packages to obtain aplurality of LED packages 1.

In this step 112, each of the LED packages 1 has the light transmittingsurface 17 formed on an upper surface of the encapsulant 10, and themetal reflective layer 20 surrounds the side surfaces of the encapsulant10 so that light from the LED chip is leaked only through the lighttransmitting surface 17.

Alternatively, as shown in FIG. 6, in the step 110 of forming thereflective layer 20 on the encapsulant 10, a sputtered layer 22′ isformed via vacuum sputtering using highly reflective metal selected froma group consisting of, for example, Al, Au, Ag, Ni, W, Ti and Pt tosurround the outer surfaces of the encapsulant 10. In this case, thesputtered layer 22′ is formed integrally with the encapsulant 10 tocompletely surround the outer surfaces of the encapsulant 10 so as notto allow any leakage of light.

In the next step 110′, an upper surface of the sputtered layer 22′ ispolished to be removed, thus forming the light transmitting surface 17on an upper surface of the encapsulant 10.

Thus is completed a structure with the light transmitting surfaces 17formed on upper surfaces of the encapsulant 10.

In the next step 112, the substrate 15 is cut horizontally andvertically into individual LED packages to obtain a plurality of LEDpackages 1.

Through the above steps, each LED package 1 is completed with the lighttransmitting surface 17 formed on an upper surface of the encapsulant 10and the metal reflective layer 20 surrounding the side surfaces of theencapsulant, thereby allowing leakage of light from the LED chip 5 onlythrough the light transmitting surface 17.

According to the present invention as set forth above, a reflectivelayer and an encapsulant are integrated to minimize the thickness of theLED package, thereby easily applicable to various types of slimmerbacklights.

In addition, the present invention does not need a molded part inaddition to an encapsulant, allowing a thin, small-sized structure, andadopts highly reflective metal for a reflective layer surrounding thesurfaces of the encapsulant, except the portion of the lighttransmitting surface, to minimize leakage of light.

In addition, in the present invention, the entire process includingmounting the LED chip, molding and dicing is conducted on a PCB,enabling mass-production with significantly improved productivity.

Furthermore, the present invention adopts EMC transfer molding using anepoxy molding compound with phosphor mixed therein so that the phosphordoes not precipitate after the encapsulant is cured, thereby minimizingirregular color distribution and significantly improving opticalquality.

Certain exemplary embodiments of the invention have been explained andshown in the drawings as presently preferred. The invention may,however, be embodied in many different forms and should not be construedas limited to the embodiments set forth herein. While the presentinvention has been shown and described in connection with the preferredembodiments, it will be apparent to those skilled in the art thatmodifications and variations can be made without departing from thespirit and scope of the invention as defined by the appended claims.

1. A light emitting diode package for emitting light from a lightemitting diode chip in one direction, comprising: a substrate with anelectrode formed thereon; a light emitting diode chip disposed on thesubstrate; an encapsulant covering the LED chip and the substrate toprotect the LED chip; and a metal reflective layer surrounding sidesurfaces of the encapsulant to form a light transmitting surface on atop surface of the encapsulant.
 2. The light emitting diode packageaccording to claim 1, wherein the metal reflective layer is formed bydepositing or plating metal selected from a group consisting of Al, Au,Ag, Ni, W, Ti and Pt.
 3. The light emitting diode package according toclaim 1, wherein the substrate comprises a printed circuit board or aceramic substrate with an electrode formed thereon.
 4. The lightemitting diode package according to claim 1, wherein the lighttransmitting surface is disposed in front and in parallel with a planewhere the light emitting diode chip is disposed.
 5. The light emittingdiode package according to claim 1, wherein the encapsulant is made ofepoxy molding compound with phosphor mixed and uniformly dispersedtherein.
 6. A method of manufacturing a light emitting diode package foremitting light from a light emitting diode chip in one direction,comprising steps of: providing a substrate with an electrode formedthereon; disposing a light emitting diode chip on the substrate; formingan encapsulant on the light emitting diode chip and the substrate;cutting the encapsulant; and forming a reflective layer on theencapsulant.
 7. The method according to claim 6, wherein the step offorming an encapsulant comprises Epoxy Molding Compound (EMC) transfermolding of transparent epoxy molding compound with phosphor mixedtherein.
 8. The method according to claim 6, wherein the step of cuttingthe encapsulant comprises dicing or etching only the encapsulant toobtain a desired form of encapsulant for the light emitting diode chip,and exposing a pattern electrode plated on the substrate.
 9. The methodaccording to claim 6, wherein the step of forming a reflective layercomprises depositing or plating metal selected from a group consistingof Al, Au, Ag, Ni, W, Ti and Pt.
 10. The method according to claim 6,wherein the step of forming a reflective layer comprises forming asputtered layer made of highly reflective metal around an outer surfaceof the encapsulant via vacuum sputtering, and removing a portion of thesputtered layer via polishing, thereby forming a light transmittingsurface.
 11. The method according to claim 6, wherein the step offorming a reflective layer includes cutting the plated reflective layerand the substrate or the sputtered reflective layer and the substrateinto individual light emitting diode packages.
 12. The method accordingto claim 7, wherein the EMC transfer molding for forming an encapsulantcomprises inserting the substrate and the light emitting diode chip in amold maintained at a temperature ranging from 150° C. to 190° C.,inserting a solid mixture of transparent epoxy molding compound andphosphor maintained at a temperature ranging from 80° C. to 90° C. intothe mold, thereby changing a phase of the mixture of transparent EMC andphosphor from solid to liquid to form an encapsulant.
 13. The methodaccording to claim 12, further comprising a step of compressing thesolid mixture of transparent epoxy molding compound and phosphor intothe mold at 500 psi to 1000 psi.
 14. The method according to claim 13,wherein the mixture is cured into the encapsulant without precipitationof the phosphor in the transparent epoxy molding compound in order tominimize irregular color distribution.